Although Candida is normally present in the vagina, Thrush occurs when the Candida overgrows, causing clinical symptoms. This often happens when the normal health of the vagina is disrupted. Almost all women get Thrush from time to time.


Epidemiology and Risk Factors
Candida is part of the lower genital tract flora in 20% to 50% of healthy asymptomatic women . Predisposing factors to Thrush include pregnancy, diabetes mellitus and the use of broad-spectrum antibiotics, and women diagnosed with AIDS. Pregnancy and diabetes mellitus are both associated with a qualitative decrease in cell-mediated immunity, which predisposes such individuals to Thrush. Antibiotic use disturbs the normal vaginal flora, decreasing the concentration of lactobacilli (a type of beneficial bacteria) and other normal flora, and thus allowing an overgrowth of Candida. Candida albicans is both the most frequent colonizer and responsible for most cases of Thrush. Nevertheless, there have been reports demonstrating an increase in the frequency of cases caused by other Candida species, predominantly Candida glabrata.

Thrush is a common infection among women, and it is estimated that as many as 75% of women experience at least one episode of Thrush during their lifetimes. Approximately 50% of women will experience second episodes of Thrush. Although the condition is rare before menarche, by the age of 25 half of all college women will have had at least one physician-diagnosed episode of Thrush. It is less common in postmenopausal women.

In 1987, infectious vaginitis was a common clinical problem that results in 5 million to 10 million office visits per year.In 1995, it was estimated that 7.9 million women had their episode of Thrush diagnosed by a physician (including a physical examination), and that 11.4 million women self-diagnosed the infection or were diagnosed by phone consultation. Over-the-counter and prescription medicines were used by an estimated 10.2 and 5.7 million women, respectively. It was estimated that the annual social cost of Thrush in 1995 in the USA was approximately US$1.8 billion. Approximately half of this annual social cost consisted of charges for physician visits, and is expected to increase to US$3.1 billion by 2014.


Clinical Manifestations
The principal symptoms of Thrush are vulva and/or vaginal itch and a thick vaginal discharge. However, these symptoms alone are not sufficiently reliable to permit correct diagnosis and treatment. The accurate diagnosis of Thrush requires both clinical and laboratory confirmation.


Specific Diagnostic Strategies
As vaginal infections may be caused by organisms other than Candida, such as trichomonas and bacteria, it is not possible to make a diagnosis based solely on a patient's history and genital examination. A patient will further need to have a pelvic examination and have a vaginal swab taken and examined under a microscope. In some cases, the vaginal swab may need to be cultured by a laboratory for diagnosis. The diagnosis of Thrush usually involves finding the normal vaginal pH (which is pH4 to pH4.5) and obtaining positive results on microscopy. However, due to the poor sensitivity of these tests and the lack of specificity of clinical signs, accurate diagnosis of Thrush is difficult, and a vaginal culture should be obtained. The above procedure may take up to a week for proper diagnosis of Thrush to be established.